At the bottom of America's electronics wastebasket lies the township of Guiyu. The cluster of villages in southern China's Guangdong province is a dumping ground for mountains of scrapped computers and high-tech appliances, the detritus of a digital revolution going on an ocean away. Blue Dongfeng trucks with heaving loads of broken hardware dominate the roads and kick dust into the faces of the bicycle-cart drivers, their own cargo of tangled wires swaying with each turn. Atop a riverbank junk heap near the Meizhou bridge, a piece of cardboard flutters in the breeze—printed on it are keystroke instructions and the...